Work machines are commonly used to excavate earth or other material from a geographic location in a work site. These work machines typically include a work implement linkage that supports a ground engaging tool, such as, for example, a bucket or shovel. A work machine operator may control the movement of the work implement linkage and the ground engaging tool to excavate earth or other material from the geographic location to shape the surface to conform to a desired surface configuration.
The work implements of these work machines are commonly powered by a hydraulic system. A typical hydraulic system includes a series of hydraulic actuators, which may be, for example, hydraulic cylinders, that are interconnected with the work implement linkage. The hydraulic system may also include a series of control valves that govern the rate and direction of fluid flow into and out of each hydraulic actuator. By coordinating the fluid flow to and from each hydraulic actuator, the overall motion of the work implement linkage and the ground engaging tool may be controlled.
An operator may control the work implement linkage on the work machine to excavate earth from a geographic location to achieve the desired surface configuration, which may be, for example, a surface having a certain slope or a trench having a certain length, width, and depth. In many cases, a substantial amount of earth, or other material, must be excavated to achieve the desired surface configuration. A number of measurements of the location of the current elevation of the surface of the geographic location may be required to determine when the proper amount of material has been excavated to achieve the desired surface configuration.
The work machine may include a positioning system to assist the operator in achieving the desired surface configuration. For example, as shown in U.S. Pat. No. 6,336,077 to Boucher, the work implement linkage of a work machine may be equipped with sensors that allow the position of the ground engaging tool to be determined. The work machine may also include a computer control that allows the operator to input a desired hole depth and an associated slope gradient leading to the hole. The computer control may further provide a display having a representation of the desired hole depth and the associated slope gradient.
However, this type of positioning system may only provide an estimate as to the location of the ground engaging tool relative to the desired hole depth or slope gradient. The system described in the '077 patent does not account for a rotation of the work implement linkage, such as when the operator activates a swing assembly on the work machine. If the rotational angle of the work implement linkage is varied and this variation is not taken into account during the positional computation, the positioning system may not correctly determine the position of the ground engaging tool relative to the desired hole depth or slope gradient.
The system and method described below solves one or more of the problems set forth above.